Apparatus for milling road surfaces

ABSTRACT

Apparatus and method for milling road surfaces wherein a motor driven rotatable roller, equipped with hard-metal cutters, is moved horizontally at a uniform level relative to the road surface, the level being such that the cutters engage the road surface during rotation of the roller. In accordance with the present invention, the roller is rotated in a direction opposite to the direction of forward movement of the axis of the roller relative to the road surface. That is, the cutters mill the road surface in a direction of forward movement of the axis of the roller. The apparatus of the invention further includes means for varying the level of the roller, and for varying the tilt of the roller relative to the road surface.

O Un ted States Patent 1191 1111 3,829,161 Wirtgen Aug. 13, 1974 APPARATUS FOR MILLING ROAD 3,407,005 10/1968 Simms et a1. 299/39 SURFACES 3,414,327 12/1968 Austin 299/39 X 3,547,492 12/1970 Blnger 299/39 Inventor: Relnhard g 5461 3,606,468 9/1971 Walker et a1. 299/39 Windhagen, Hohner Strasse Germany Primary Examiner-Ernest R. Purser 22 Filed; Aim 17 1972 Attorney, Agent, or Firm-Flynn & Frishauf 21 A 1. N 244775 1 1 PP 0 1 57 ABSTRACT Apparatus and method for milling road surfaces [30] Fomgn Apphcatlon Pnomy Data wherein a motor driven rotatable roller, equipped with Apr. 16, 1971 Germany 21 18458 hard meta1 Cutters, is moved horizontally at a if Sept- Germany 6 2145497 level relative to the road surface, the level being such 1972 Germany 2203529 that the cutters engage the road surface during rota- Jan. 26, 1972 Germany 2203530 tion of the m In accordance with the present vention, the roller is rotated in a direction opposite to UIS. CL 1 th di ti f f d movement f th i f th [51] lift. Cl. E016 23/09 roller relative to the d Sudacfi h is, the cutters [58] Field of Search 299/10, 39, 18 n the road surface in a direction of forward move ment of the axis of the roller. The apparatus of the in- [56] References cued vention further includes means for varying the level of UNI D A S T S the roller, and for varying the tilt of the roller relative 1,883,404 10/1932 Ronning 299/39 x to the road surface. 2,062,232 11/1936 Pogue 2,817,275 12/1957 Lenker 9 Clam, 7 Drawmg Flgures 3,072,391 McDarrah 299/39 I I 6 12 w o a PATENIED Aum 31914 SHEEI 3 BF 6 APPARATUS FOR MILLING ROAD SURFACES The present invention relates to apparatus and a method for milling road surfaces, and more particularly to milling road surfaces made from concrete, asphalt, or the like.

The use of spiked tyres during the winter months is to an increasing extent leading to unequal wear of the surfaces of highways and motorways in particular. Attempts to repair this damage is proving extraordinarily difficult, especially since a localised improvement simply does not prove permanent and, from a practical point of view, is not even feasible.

Attempts have already been made to repair localised damage, particularly in the constantly used inside lane, by removing a layer over the whole road surface up to a depth of 2 cm., for example, in order that a regular surface can be obtained which can then be fully recoated, if so required.

Removing a uniform amount from the road surface is, however, very difficult and above all expensive.

With asphalt or bituminous surfaces there has already been developed for this purpose, a method whereby the surface is preheated by gas burners and then a layer of a predetermined depth is removed by means of plane or cutter-like implements. Such a method, however, is extraordinarily time-consuming and extensive in particular because of the prolonged pre-heating and has not proved successful in practice.

In addition, attempts have also been made to carry out the removal without the time-consuming preheating and to tacklethe road-surfacings of asphalt or concrete directly by means of cutter-like tools and thus remove the required amount of material. Devices have already been developed to carry out this method, which devices consist of a chassis, preferably provided with its own drive mechanism, and a motor-driven roller equipped with tungsten carbide cutters, said roller being mounted horizontally in relation to the road surface and vertically adjustable. The width of the cutter roll is approximately the same or less than the total width of the machine.

By means of the cutter roller rotating in the direction of travel a definite amount of road surfacing is removed by the carbide cutters mounted on the cutter roller and is scooped up behind the roller. Although the results obtained by this method are relatively good, the amount of wear on the carbide cutters has proved enormously high and is an economic stumbling block in the use of such a cutting machine.

Continuous developments in the realm of materials do make new and harder alloys available for the hardmetal cutters, but unfortunately the more the hardness increases the less the flexibility and toughness of the material, with the result that these materials are no longer suitable for use in the above-described cutter mechanism since the cutters break up too easily.

in addition, practical experience with such a cutter mechanism has shown that in particular with relatively hard road surfaces there occurs relatively high vibration in the whole cutter mechanism which leads to an increased load on the cutters and irregular cutting away of the road surface.

The aim of the present invention is to create a method and mechanical means by means of which the wear on the cutters is reduced and in addition the use of very hard modern cutter materials is made possible. in addition, a more regular cutting effect is to be ob tained which is ensured even when the cutting width is large.

It was found that the wear on hard-metal cutters can be considerably reduced, and that hard-metal cutters in particular, of extraordinary hardness but with the reduced toughness unfortunately associated with this, can be used if the cutter roller of the above-described cutting device is not rotated as previously in the forward direction of travel of the chassis, but if the direction of travel of the roller is the opposite of the direction of travel of the chassis.

It is not an obvious step to utilise an opposite direction of rotation of the cutter roller since in so doing the cut material is not stored behind the cutter roller but in front of same and thus offers an impediment to the forward movement of the chassis and thus to the cutter rolleritself.

Surprisingly enough this is in fact only an apparent disadvantage since the cut-up material is stored to only a certain depth in front of the cutter roller. If this depth is exceeded the cutter roll then operates as a conveyor roller as well and transports the cut material backwards over the roller (viewed in the direction of travel) where it is stored and if necessary caught by one or more pusher blades which are mounted on the chassis behind the roller, and gathered together or transported at the side.

This surprising and completely unexpected result, obtained by reversing the direction of rotation of the cutter roller, as regards resistance to wear of the hardmetal cutters being used and'in particular as regards the possibility of using significantly harder cutters which are nonetheless less resilient and tough, canonly be explained by the different cutting angle of the cutters in relation to the road surface. If the cutter roller rotates in the direction of the forward movement of the chassis then the cutters mounted on the roller meet the road surface to be milled at a relatively obtuse angle. This relatively obtuse impact requires a high degree of resilience and toughness on the part of the cutter material in order to prevent the break-up of the cutter. For this reason extremely hard cutter materials are not suitable.

By reversing the direction of rotation of the cutter roll the operating or impact angle at which the individual cutters of the cutter roll meet the road surface is altered. Since each cutter so to speak comes into play in the tracks of its predecessor each cutter meets the roadway to be removed at a very acute angle with the result that any obtuse impact on the roadway is avoided. This has the result that such great stresses re garding resilience and toughness are no longer placed on the cutter material and consequently considerably harder cutters can be used. The life of such cutters is however much greater with the result that from an economic point of view there are considerable benefits to be derived, and the method of the invention can now be put into use to its maximum extent under economically favourable conditions.

It has proved advantageous if, in the case of the method of the invention the speed of rotation of the roller amounts to between 60 and 140 rpm. A speed of about revolutions per minute is particularly advantageous.

The diameter of the cutter roller is preferably 50 to 80 cm. A more uniform surface is obtained if, in accordance with a special embodiment of the mechanical means of the invention, the cutters on the cutter roller are mounted helically.

A further improvement of the cutting effect, and in particular, uniform removal of material, is obtained by providing the cutter roller at both its terminal securing points with one or more support wheels resting directly upon the road surface.

In this way any vibrations arising in the chassis are completely avoided and there is thus obtained a hitherto unattainable accuracy of cut.

The support wheels mounted on the two end bearings of the roller are designed in accordance with a particularly advantageous embodiment of the present invention with vertical adjustment in relation to the bearings. Such vertical adjustment can be obtained appropriately by means of elevating screws. It is also possible, naturally, to use hydraulic jacking cylinders. The jack screws have proved to be particularly advantageous because they enable precise vertical adjustment of the support wheels in a simple manner.

The support wheels are preferably mounted laterally beside the cutter roller at its mounting supports.

In order to enable the road surfaces to be dealt with right up to the edge, in particular it has been proved advantageous for the support wheels to be mounted in front of the roller at its support mountings, viewed from the direction of travel.

According to a particularly advantageous embodiment the support wheels are secured behind the roller (viewed from the direction of travel) at its mountings. The support wheels thus rest on the completely level road surface which has already been milled, with the result that these wheels which are ultimately responsible for the precise guidance of the cutter roller, guide the roller at a constant distance over the road surface.

Since the support wheels are secured directly to the support mounting r bearing of the cutter roller and rest firmly on the road surface all vibrations during operation of the cutter roller are reliably avoided and this is true even on very hard road surfaces, for example those made from concrete.

The support wheels are preferably designed as solid rubber tyres or steel wheels. In this way any unnecessary vibration is completely excluded which might have an adverse effect on the cutting properties of the roller.

If the support wheels, viewed from the direction of travel, are mounted behind the cutter roller, then it has been proved to be particularly useful for one or more pusher blades to be mounted in front of the support wheels to remove the cut material. In this way there is no risk of the cut material interfering with the regular passage of the support wheels and in this way the vertical adjustment of the roller in relation to the smoothly milled road surface is not adversely affected.

The support wheels are normally secured as single wheels to the two support mountings for the cutter roller. The stability of the whole cutting mechanism is, however, further increased if the support wheels mounted on each side are connected to each other by a common axle.-

The application pressure of the support wheels on the road surface can be regulated by means of the vertical adjustment device for the cutter roller and if necessary the whole weight loading the front wheels of the chassis can, practically speaking, be shifted to the suppo wheels.

When cutting away the edges of road surfacings difficulties can arise inasmuch as the wheels on one side of the chassis, lying one behind the other, may run along the hard shoulder or the pavement whilst the wheels on the other side of the chassis are still on the roadway itself. The whole machine is thus tilted along its longitudinal axis and the cutter roll then runs at an acute angle to the road surface level.

To avoid this drawback it has proved appropriate, according to another embodiment of the present invention if the cutter roller forms a single constructional unit with the driving gear, which unit is connected by a drive shaft to the drive motor and is secured by mounting brackets, which can be provided with vertical adjustment if necessary, directly or indirectly to the chassis. In this case it is particularly advantageous if the construction unit is secured directly or indirectly to the chassis by a three-point suspension mounting. Such a vertically adjustable three-point suspension makes possible, in the simplest possible manner, tilting of the construction unit at an angle to the direction of travel, with the result that the above-mentioned irregular removal action is avoided.

For the three-point suspension it is preferable to use cardan-type mountings of which at least one is designed with vertical adjustment. If both suspensions arranged above the cutter roller are designed with vertical adjustment, for example by using screwed jacks, hydraulic cylinders or the like, it is possible to effect adjustment of the cutting depth by these vertically adjustable means at the same time. This happens in this case, in that both vertical adjustments are lowered by the same amount.

Different adjustment of the two suspensions mounted above the cutter roller produces in this case the desired tilting of the cutter roller. For practical operation, however, it has proved best if the cutting depth adjustment takes place independently and is not effected by the suspension mountings operating the tilting of the cutter roller. According to another embodiment the unit with its optionally vertically adjustable suspensions is secured by an independently vertically adjustable support mounting to the chassis.

This independently vertically adjustable support mounting thus permits adjustment of the cutting depth.

The economic viability of the inventive device depends on the width of the cutter roller. For this reason every effort has been made to use the widest possible cutter rollers. There is the consequent disadvantage however, than when the cutter roller width exceeds the standard machine width, difficulties arise in transport.

This disadvantage is avoided, according to a further embodiment of the present invention, in that the construction unit is secured, so that it can swivel round a vertical axis, by means of its suspensions through an independently vertically adjustable support beam in a ring mounting secured to the chassis.

Such a swivel arrangement of the unit makes it possi ble, in particular with very broad cutter rollers, to swivel the unit round on the vertical axis once the universal shaft operating the drive between the motor and the gear mechanism in the unit is released.

The swivelling of the unit can be effected either manually or by a motor which is particularly advantageous. It has proved most useful to use a hydraulic gear motor for lowering the support beam since this type of motor is better adapted than an electrical geared motor to cope with the harsh working conditions.

In order to ensure that the cutter roller or rollers come to rest with their axis perpendicular to the longitudinal axis of the machine during the motorised lowering of the unit, from the position adapted to the travelling operation to the final cutting position, it is recommended, at least in the position appropriate to the cutting operation, that limit switches should be fitted to the unit and operated by same, which switches act on the one hand on the control circuit of the hydraulic gear motor and on the other hand on safety means which forbid accidental lowering of the support beam.

The exemplified embodiments shown in the accompanying drawings serve to further explain the invention. These drawings show:

In FIG. 1, a side view of mechanical means according to the invention for the milling of road surfaces, which is provided with the support wheels mounted on the end support mountings of the cutter roller and rest themselves on the road surface.

In FIG. 2, an enlarged drawing of the cutter roller equipped with hard metal cutters and their action on the road surface which is to be milled.

In FIG. 3, a side view of a machine in which the cutter roller is connected with the gearing to form a single construction unit.

In FIG. 4, a perspective view of the unit with its suspension, as in FIG. 3.

In FIG. 5, a perspective view of a unit with a different suspension.

In FIG. 6, a side view of mechanical means according to the invention in which the construction unit is mounted so that it can swivel around a vertical axis in a ring mounting. a

In FIG. 7, a top view of the ring mounting in FIG. 6.

The inventive mechanical means shown in FIG. 1 comprises a chassis l with a steerable pair of front wheels 2 and rear wheels 3 which are propelled forward by a motor 4 which also drives the cutter roller 7 through the universal shaft 5 and the transmission 6. The vertical adjustment'of the cutter roller 7 is effected by the support mounting 8 and the hydraulic cylinder 9.

The direction of rotation of the cutter roller 7 is shown by the arrow and is opposite to the direction of movement of the chassis. This means that the cutmaterial 10 assembles in front of the cutter roller up to a certain height and is then transported to the rear by this roller. The direction of forward movement of the chassis 1 can be seen from the arrows which are located at the front and rear wheels.

In FIG. 2 the cutter roller 7 and the action of the hard metal cutters 11 mounted thereupon on theroad surface are shown in enlarged detail.

From this figure the acute operating angle of the hard metal cutters on the road surface can be clearly seen.

Viewed from the direction of travel of the cutter roller, the cut material gathers, as shown also in FIG. 1, in front of the cutter roller and is finally, when it has reached a preset height, transported to the rear over the roller by the hard metal cutters 11 acting as conveyor elements.

On the support mountings 8, viewed from the direction of travel which are in front of the cutter roller 7, a support wheel 12 is mounted on each side which is guided with vertical adjustment by means of a screwed jack 13.

This support wheel 12 can, according to another em bodiment of the present invention in which it is again viewed from the direction of travel, be mounted behind the cutter roller at the appropriately shaped mounting. The mounting can, naturally, also be effected on the inside face of the support mounting and it is simply for the sake of better illustrating the arrangement that it is secured, in the example shown, on the outside of the cutter roller mounting.

In the embodiment shown in FIGS. 3 and 4 the construction unit 14 is mounted between the front pair of wheels 2 and the rear pair 3. This unit comprises basically a cutter roller 7 fitted with chisel-like cutters which is driven by the diesel motor 4 through a gear system 15 (see FIG. 4) and a universal shaft 5. Naturally it is also possible to provide, for the cutter roller drive, an additional motor on the chassis 1 or inside the unit 14.

The cutter roller 7 is, as can be seen from FIG. 4 in particular, mounted along with its shaft 16 in a frame 17 which comprises two side pieces 18 and 19 and two crossbeam supports 20 and 21 connecting same, with the frame 17 being suspended directly on these sup ports to the chassis 1. In the rear part of the frame 17 is located the gear system 15 whose drive shaft or shafts 22 and 23 depending on the design of the gear system 15 used are also mounted in the side pieces 18 and 19. On the ends'of the shaft 22 and 23 adjacent to the side pieces 18 and 19 is located on each side a sprocket wheel 24 or 25 which drives through a chain 26 or 27 a sprocket wheel 28 or 29 secured to the cutter roller shaft 16. The input shaft 30 of the gear system 15 is connected, as already mentioned, to the diesel motor 4 through the universal shaft 5. The cutter roller 7 mounted in the frame 17 and the gear system 15, which together form the construction unit 14, can be swivelled around an almost horizontal axis 31 located in the mid-plane perpendicular to the cutter roller axis, on a support mounting 32, and around an axis 33 parallel to the axis 31 on another support mounting 34 to form a pivoting arrangement. The support mounting 32 is welded to the support panel of a carrier beam 39 comprising four panels 35, 36, 37 and 33 and comprises either a relatively broad mounting in the axial direction or two support mountings mounted at the front and rear end of the construction unit. The locking arm 34 is the piston rod of a hydraulic piston drive system 40 which is mounted on the support panel 37 so that the locking arm 34 thus operates in conjunction with the support beam 39. The support 39 is, as is particularly apparent from FIG. 3, displaceably secured by means of two arms 41 and 42 to the chassis 1 and can be swivelled by means of another hydraulic piston drive system 43, which is located on a reinforcing rib 44 of the chassis 1 and whose piston rod 45 is swivelmounted to the support panel 35, around the axis 46,

by which means the cutting depth can be regulated. By controlling the hydraulic piston system 40 the adjustment of the desired tilt to the cutter roller 7 in relation to the horizontal can be obtained.

ln FIG. is shown another possible means of suspending the construction unit 14 comprising the cutter roller 7 mounted in the frame 17 and the gear system. In this case the unit is suspended in the mid-plane perpendicular to the cutter roller axis on a universal coupling 47 engaging with the crossbeam 21 on a reinforcing strut 48 screwed directly to the chassis l and vertically adjustable with its crossbeam 20 and inclinable to the horizontal on a support mounting 49 swivel mounted around its longitudinal axis on the chassis 1. To adjust the height or depth of cut and the cutter roller tilt two hydraulic piston drives 50 and 51 are provided on the support mounting 37 whose piston rods 52 and 53, acting as support arms, are swivel mounted on the crossbeam 20. Such an embodiment is obviously less expensive to construct than the one initially men 'tioned. It can be further simplified in that one of the two piston drives 50, 51 is replaced by a swivelmounted support rod whose length cannot be altered,

with the result that the inclination of the construction unit is effected simply by regulating one hydraulic piston drive.

In the embodiment shown in F 168. 6 and 7 theconstruction unit 14 is located between the front wheels 2 and the rear wheels 3, said unit comprising a cutter roller 7 with a plurality of chisel-like cutters (not shown) which operates in conjunction with the diesel motor 4 through a gear system 15 and a universal shaft 5. Instead of the diesel motor 4 an additional motor can be provided to drive the cutter roller 7 either on the chassis l or the construction unit 14. The width of the cutter roller is considerably greater than the overall width of the chassis.

The cutter roller 7 and the gear system 15 are combined to form one single unit inside a frame 17 in which the cutter roller 7 with its shaft 16 and drive shafts 22 and 23 of the gear system 15 are mounted. On each of the drive shafts 22 and 23 is located, as can be seen from FIG. 7, a sprocket wheel 24 or 25 which is connected by a chain 26 or 27 to a sprocket wheel 28 or 29 secured to the cutter roller shaft 16.

For regulating the height or cutting depth of the cutter roller 7 the frame 17 forms an articulated link at its front end, adjacent to the cutter roller 7 at the piston rod 54 of a hydraulic piston drive 55, and at its rear 'end, opposite the cutter roller 7, to a support arm 56.

The other end of the support arm 56 is welded to one end ofa support 57. To the other end of the support 57 is fitted the cylinder 58 of the hydraulic drive 55.

On the two longitudinal spars 59 and 60 of the chassis 1 is provided a ring mounting 61 which is screwed at its lower part 62 to the spars 59 and 60 and on the upper rotary part 63 of which the support 57 rests. The rotation of the upper part 63 of the ring mounting 61 is effected by a hydraulic geared motor 64.

As already mentioned, the driving shaft 65 of the gear system 15 is connected by the universal shaft 5 to the diesel motor 4 of the mechanism. Since before any rotation of the support 57 from the cutting position this connection has to be released and then remade after rotating back, the universal shaft 5 is divided into two parts at and 5b which can be connected to one another to form a positive connection by means of a coupling 66. The coupling 66 comprises, as can be seen from H6. 7, an internal square 67 which is welded on to the part 5a, and an appropriately dimensioned outer square 68 which is machined by milling out of the part 512. The dimensions of the outer square 68 and those of the internal square 67 are so selected that easy inwards and outwards movement, for engagment of the two parts, is ensured.

Whilethe invention has been described with respect to specific embodiments, it should be clear that various modifications and alterations can be made to the structural arrangement without departing from the inventive concept set forth in the accompanying claims.

1 claim:

1. Apparatus for milling road surfaces comprising:

a movable motor driven chassis;

a rotatable roller carrying hard-metal cutters thereon;

means, including a drive system driven by the motor driving said chassis, for rotating said roller in a direction of rotation such that the underside of said roller moves forward more rapidly than the forward advance of said chassis, said cutters engaging and milling said road surface during rotation of said roller when the roller is lowered into operating position, and

suspension mounting means comprising a three point suspension for coupling said roller and drive system as a single unit to said chassis and for raising, lowering and vertically adjusting said roller.

2. Apparatus according to claim 1 wherein said suspension mounting means comprise at least one vertically adjustable mounting and a further two cardantype suspension mountings.

3. Apparatus according to claim 2 wherein said single unit comprising said roller and drive system includes vertically adjustable suspension members mounting said roller thereto, said single unit being connected to said chassis by an independently vertically adjustable support mounting.

4. Apparatus according to claim 3 wherein said single unit comprising said roller and drive system is pivotally mounted to said chassis, said independently vertically adjustable support mounting pivoting said single unit during adjustment thereof.

5. Apparatus for milling road surfaces comprising:

a movable motor driven chassis;

a rotatable roller carrying hard-metal cutters thereon;

means, including a drive system driven by the motor driving said chassis, for rotating said roller in a direction of rotation such that the underside of said roller moves forward more rapidly than the forward advance of said chassis, said cutters engaging and milling said road surface during rotation of said roller when the roller is lowered into operating position, and

suspension mounting means for coupling said roller and drive system as a single unit swivel mounted around a vertical axis to said chassis by means of a ring mount secured to the chassis and providing for raising, lowering and vertically adjusting said roller.

6. Apparatus for milling road surfaces comprising:

a movable motor driven chassis;

a rotatable roller carrying hard-metal cutters thereon;

means, including a drive system driven by the motor driving said chassis, for rotating said roller in a direction of rotation such that the underside of said roller moves forward more rapidly than the forward advance of said chassis, said cutters engaging and milling said road surface during rotation of said roller when the roller is lowered into operating position, and

means for mounting said roller approximately horizontal to said chassis with said roller being vertically adjustable in relation to the road surface, said mounting means including a frame structure carrying said roller, said frame structure being connected to said chassis so as to pivot universally about a pivot affixed to said chassis.

7. Apparatus according to claim 6 including means for pivoting said frame structure to adjust the height of said roller relative to the road surface.

8. Apparatus according to claim 6 including means for pivoting said frame structure to adjust the tilt of said roller relative to the road surface.

9. Apparatus for milling road surfaces comprising:

a movable motor driven chassis;

a rotatable roller carrying hard-metal cutters thereon;

means, including a drive system driven by the motor driving said chassis, for rotating said roller in a direction of rotation such that the underside of said roller moves forward more rapidly than the forward advance of said chassis, said cutters engaging and milling said road surface during rotation of said roller when the roller is lowered into operating position, and

means for mounting said roller approximately horizontal to said chassis with said roller being vertically adjustable in relation to the road surface, said mounting means including a first frame structure carrying said roller, said frame structure being pivotally connected to a second frame structure pivoted on said chassis, said first frame structure being pivoted to swing at right angles to the pivotal swing of said second frame structure, each said frame structure being provided with vertical adjusting means for adjusting its position about its pivot relative to the member on which it is pivoted. 

1. Apparatus for milling road surfaces comprising: a movable motor driven chassis; a rotatable roller carrying hard-metal cutters thereon; means, including a drive system driven by the motor driving said chassis, for rotating said roller in a direction of rotation such that the underside of said roller moves forward more rapidly than the forward advance of said chassis, said cutters engaging and milling said road surface during rotation of said roller when the roller is lowered into operating position, and suspension mounting means comprising a three point suspension for coupling said roller and drive system as a single unit to said chassis and for raising, lowering and vertically adjusting said roller.
 2. Apparatus according to claim 1 wherein said suspension mounting means comprise at least one vertically adjustable mounting and a further two cardan-type suspension mountings.
 3. Apparatus according to claim 2 wherein said single unit comprising said roller and drive system includes vertically adjustable suspension members mounting said roller thereto, said single unit being connected to said chassis by an independently vertically adjustable support mounting.
 4. Apparatus according to claim 3 wherein said single unit comprising said roller and drive system is pivotally mounted to said chassis, said independently vertically adjustable support mounting pivoting said single unit during adjustment thereof.
 5. Apparatus for milling road surfaces comprising: a movable motor driven chassis; a rotatable roller carrying hard-metal cutters thereon; means, including a drive system driven by the motor driving said chassis, for rotating said roller in a direction of rotation such that the underside of said roller moves forward more rapidly than the forward advance of said chassis, said cutters engaging and milling said road surface during rotation of said roller when the roller is lowered into operating position, and suspension mounting means for coupling said roller and drive system as a single unit swivel mounted around a vertical axis to said chassis by means of a ring mount secured to the chassis and providing for raising, lowering and vertically adjusting said roller.
 6. Apparatus for milling road surfaces comprising: a movable motor driven chassis; a rotatable roller carrying hard-metal cutters thereon; means, including a drive system driven by the motor driving said chassis, for rotating said roller in a direction of rotation such that the underside of said roller moves forward more rapidly than the forward advance of said chassis, said cutters engaging and milling said road surface during rotation of said roller when the roller is lowered into operating position, and means for mounting said roller approximately horizontal to said chassis with said roller being vertically adjustable in relation to the road surface, said mounting means including a frame structure carrying said roller, said frame structure being connected to said chassis so as to pivot universally about a pivot affixed to said chassis.
 7. Apparatus according to claim 6 including means for pivoting said frame structure to adjust the height of said roller relative to the road surface.
 8. Apparatus according to claim 6 including means for pivoting said frame structure to adjust the tilt of said roller relative to the road surface.
 9. Apparatus for milling road surfaces comprising: a movable motor driven chassis; a rotatable roller carrying hard-metal cutters thereon; means, including a drive system driven by the motor driving said chassis, for rotating said roller in a direction of rotation such that the underside of said roller moves forward more rapidly than the forward advance of said chassis, said cutters engaging and milling said road surface during rotation of said roller when the roller is lowered into operating position, and means for mounting said roller approximately horizontal to said chassis with said roller being vertically adjustable in relation to the road surface, said mounting means including a first frame structure carrying said roller, said frame structure being pivotally connected to a second frame structure pivoted on said chassis, said first frame structure being pivoted to swing at right angles to the pivotal swing of said second frame structure, each said frame structure being provided with vertical adjusting means for adjusting its position about its pivot relative to the member on which it is pivoted. 